Can Bernie Sanders win the general election for President if he is nominated by the Democratic party? I don’t know the answer, but I do know that the many opinion pieces I’ve read since the Nevada primary illustrate the worst features of expert commentary. Professor Philip Tetlock of Wharton has detailed these in his booksExpert Political JudgementandSuperforecasting. Experts are less accurate than simple random methods.

On the other hand, other simple methods, developed via painstaking empirical research and psychological insight over many years, do work.

The question is of great importance to the many Democrats whose main desire is anyone-but-Trump. If Sanders has no realistic chance, it will take immediate strong efforts to stop Sanders—efforts that are likely to alienate many progressive Democrats and possibly swing the election to Trump. But if the answer is that Sanders can win, the best strategy to beat Trump is likely to get behind the winner as quickly and solidly as possible to build the unity the party needs to get the donors, volunteers and voters it needs to win.

But right off the bat there is a problem. The answer is probably not a clear yes or no. Experts get recognized as experts by having strong opinions. While they may offer a few disclaimers early in op-ed pieces about how anything can happen, the tone of the ones I have read suggests the clear weight of the evidence is on one side or the other of this question. To make an intelligent strategic decision, knowing the amount of uncertainty around the answer is crucial.

Another problem is experts have to appear smart, so they jump in with all kinds of smart insights. You don’t actually need a particularly high IQ or detailed familiarity with election modeling to come up with long lists of smart-sounding reasons on either side, so you get to pick whichever answer suits you.

Accurate forecasting requires starting dumb. Before you focus your awesome mental powers onsubtleties of a problem, start with a reasonable baseline. This gives you some solid ground from which to explore. Without it you’re like someone closing her eyes and sticking a pin in a map, then doing detailed geographic research of whatever place you hit. Start by looking at the whole map, without detailed geography or preconceived clever points.

In this case the obvious starting point is asking how often challengers unseat incumbents in US Presidential elections? The answer is 9 times in 29 attempts. Since 1900 it’s 4 times in 17 attempts, which is probably more relevant to 2020. So we’re starting with something that does happen, but more often does not. Of course, this applies to any Democratic candidate, we haven’t started thinking about Sanders yet.

Looking a little deeper, the 25% most lop-sided of those 29 elections all went to the incumbent. So challengers can lose in landslides, incumbents never have. Compare the upset winners: Franklin Roosevelt over Herbert Hoover, Jimmy Carter over Gerald Ford, Ronald Reagan over Jimmy Carter and Bill Clinton over George H. W. Bush; to the landslide losers against incumbents since 1900: Alf Landon to Franklin Roosevelt, Barry Goldwater to Lyndon Johnson, George McGovern to Richard Nixon and Walter Mondale to Ronald Reagan. Is Sanders more like FDR, Carter, Reagan and Clinton; or more like Landon, Goldwater, McGovern and Mondale?

While I don’t think the answer is entirely clear-cut, on balance Sanders seems more like the losers than the winners. He’s a Senator, like the three most recent losers, as opposed to an ex-governor like the four winners. A challenger to an incumbent has to demonstrate competence, and voters seem to trust experience running a State over a career talking about national and international issues. Two of the winners, Carter and Clinton, were on the side of their party closer to the center, while FDR and Reagan were on the side away from the center. Sanders, like all four landslide losers—but also two winners—is on the side away from the center.

Three of the winners benefitted from disasters in their opponents’ first terms: the Great Depression for FDR, Watergate and the oil crisis for Carter, stagflation and the hostage crisis for Reagan. Only Bill Clinton beat an incumbent who wasn’t laboring under a massive burden.

Of course, there could be a disaster for Trump before the election, but if that’s what Sanders needs, any Democrat would win in that case. So it’s not really Sanders winning the election, but Trump losing it. For strategic planning purposes, it doesn’t make sense to consider this. Also, three of the landslide losers had burdened opponents: the continuing Depression didn’t help Landon, the Vietnam War didn’t win for Goldwater, and Watergate, Kent State and escalation in Vietnam and Cambodia weren’t enough to prevent McGovern from getting buried.

Thinking about this, I arrive at a baseline that says a Sanders victory would be pretty much unprecedented—a Senator from the wing of his party farther from the center beating an incumbent not saddled with major disaster. We have examples of candidates like that losing in landslides, and most lose in close elections, but no examples of them winning.

Unprecedented doesn’t mean impossible. In a movie someone will say, “There’s gotta be a first time.” No, there doesn’t. But there can be a first time.

Now we see the value of the baseline. Because we’re looking for an unprecedented event, we have to think about what’s different about Sanders and this election. It doesn’t seem likely that he’ll win like Clinton did, or like Reagan, Carter or FDR, he’ll need to find a new way. If he doesn’t, it’s pretty easy to picture him losing like Landon, Goldwater, McGovern or Mondale.

Trump is one obvious novelty. We’ve had some dishonest or nasty Presidents, but none have lied with the recklessness of Trump, nor bullied so openly. But this doesn’t move the baseline for me. The problem is Trump won in 2016 with his qualities on open display. He’s done pretty much what he promised, more so than any other President in recent memory. People who voted for him in 2016 overlooked those qualities, and also voted for someone many people predicted would destroy the economy, sabotage our foreign policy and do other terrible things.

Things have gone pretty well objectively, especially if you’re inclined to Trump’s political stance (assuming you can figure out what it is). He’s also delivered for Republicans outside his base with his Supreme Court and executive branch appointments. It’s hard to see anyone who voted for him in 2016 switching to Sanders, and a lot of people who refrained from voting for him out of fear, should support him this time. He could pick up votes from Republicans who stayed home in 2016.

Also, a lot of centrists who could accept Hillary Clinton might find Sanders too radical and vote for Trump or stay home or vote third party. I don’t think Sanders can win by exploiting dislike of Trump, it’s a weaker weapon in 2020 than in 2016, and weaker for Sanders than Clinton, and it didn’t win for Clinton.

The Democrat’s gains in the midterm could be another source for optimism for Sanders. But I don’t see that either. FDR and Carter had big midterm gains, bigger than the 2018 gains, but Reagan and Clinton won despite their parties picking up only a few House seats in the prior midterm. And big midterm gains didn’t help Thomas Dewey, Walter Mondale, Bob Dole or Mitt Romney. So midterms gains do not seem to predict challenger victory.

Another problem with these last two arguments is they apply equally to all Democrats. The relevant question isn’t can Sanders win, but can Sanders win any election that wouldn’t be won by any Democrat?

The one Sanders specific argument I can think of is new voters. Sanders has great support among the young, and arouses enthusiasm in groups who have not always turned out for Democrats in great numbers. Perhaps with the full support of the Democratic party, Sanders can pick up most of Hillary Clinton’s votes, plus enough new voters to put him over the top.

To my mind, here is where we can use expert help. Now that we have a baseline, we’ve reasoned from a general subjective question to a reasonably objective question about election modeling. How many new voters does Sanders need to get in which States to get more electoral votes than Trump?

I’m not an expert in this, but I have looked at the State-by-State numbers. Many of Sanders’ likely new voters are in States Democrats have won in all five of the last Presidential elections, and there are also sizeable numbers in States Republicans have always won. These are probably not going to help Sanders.

When I look at States in contention—or that have to be in contention for Sanders to have a chance—I don’t see many where plausible new voters outweigh losses due to Trump’s incumbency, the fact that things have not pretty well instead of the disaster his critics predicted in 2016, and the baggage of socialism, age, health and attack ads.

But I freely admit I could be wrong on this last point. I could be wrong on all of this, but I’m more confident about the general stuff. Someone with detailed polling data and a good model might demonstrate that Sanders has a strong chance of attracting enough new voters in the right places to win. Until I see that however, I think it’s fair to regard Sanders as a longshot, more likely to lose by a landslide than to win, and whose main chances of winning are Hail Mary plays that would win for any Democrat.

So if you don’t want Trump in 2020, figure out how to stop Sanders without tearing the party apart, or practice praying.